The most common cause of death following portasystemic shunt in patients with cirrhosis and portal hypertension is liver failure. Liver failure not infrequently occurs following diversion of portal blood from the liver by the shunt. The relationship between preoperative portal vein blood flow and total hepatic blood flow and the clinical response to a given portasystemic shunt is not understood because of the lack of appropriate techniques for portal vein blood flow determination and the inherent difficulties with techniques of total hepatic blood flow determination in cirrhotic patients. Determination of pre-shunt portal vein blood flow is of particular importance at this time because of the recent development and application of newer types of hemodynamically different portasystemic decompressive procedures. Using techniques now available, complete assessment of hepatic blood supply by direct methods without interference of portasystemic collaterals is feasible. Changes in hepatic metabolism are being investigated in response to both forms of portal decompression in view of the recently demonstrated metabolic superiority of distal, selective shunts. The relationship of preoperative and postoperative portal vein blood flow to postoperative morbidity (liver failure) and mortality is being studied in patients randomized into groups in which either mesocaval (Drapanas) interposition or selective distal splenorenal (Warren) shunt is performed.